The present invention relates generally to accelerator pump systems, and more particularly to an accelerator pump assembly which is capable of varying the amount of fuel discharged therefrom and, accordingly, the fuel discharging characteristics thereof in response to changes in ambient temperature. The invention is particularly concerned with an accelerator pump system of the type which includes a pump cylinder having an intake port communicated with a float bowl and a discharge port communicating with a pump jet.
In the operation of an internal combustion engine for motor vehicles, acceleration of the engine is effected by the depression of an accelerator pedal in order to open the throttle valve of the carburetor of the engine. Rapid opening of the throttle valve will permit a sudden inflow of air. As a result, there occurs a sudden demand for additional fuel in the carburetor because the air-fuel mixture charge of the carburetor becomes temporarily leaner. Carburetors are usually provided with an accelerator pump system in order to provide this extra fuel. However, in prior art systems disadvantages have occurred in that, because a pump plunger is linked to a throttle lever in a thermally rigid or unresponsive manner, the stroke of the pump plunger and its lever ratio are maintained constant at all times, regardless of changes in ambient temperature, with the result that fuel of an amount proportionate to the throttle opening is injected through the pump jet or the acceleration nozzle of the system without provision for the change in ambient temperature conditions.
For this reason, at low ambient temperature there results a mixture charge which is leaner than the optimum mixture charge which would be desired. Further, at higher ambient temperatures, there results a mixture charge which is richer than the optimum mixture charge desired. In either case, the proper and optimum operation of the engine is adversely affected, with a resulting increase in the amount of harmful or obnoxious constituents of the exhaust gases being emitted from the engine.
Of course, such a result is not desirable from the viewpoint of emission control of the vehicle.
Accordingly, it is an object of the present invention to provide an accelerator pump system for use with the carburetor of a motor vehicle which may vary the amount of fuel discharged into the carburetor, and consequently vary its fuel discharging characteristics, in response to changes in ambient temperature.
A further object of the invention is to provide an accelerator pump system which may deliver an optimum amount of additional fuel into the air-fuel mixture of the carburetor when the throttle valve of the engine with which it is associated is opened for acceleration. In this manner, the invention is intended to operate to reduce the amount of harmful constituents of exhaust gases which are emitted from the engine of a motor vehicle.